1. Field of the Invention
The present invention relates to a cooling water passage structure for connecting cooling water passages in cylinders forming a V-shape in a water cooled type V-shaped internal combustion engine.
2. Description of Background Art
A conventional cooling water passage structure for connecting cooling water passages in cylinders forming a V-shape in a water cooled type V-shaped internal combustion engine is described in Japanese Utility Model Publication No. 6-3142.
The cooling water passage structure described in this publication is shown in FIG. 10 wherein a V-shaped space 03 is defined between opposed cylinders 01 and 02, and cylindrical portions 04 and 05 project from the cylinders 01 and 02 into the V-shaped space 03 so as to extend in one straight line. The cylindrical portions 04 and 05 communicate with cooling water passages 06 and 07 in the cylinders 01 and 02, respectively. A connecting pipe 08 is engaged with the outer circumferential surfaces of the opposed cylindrical portions 04 and 05. O-rings 09 are interposed between the inner circumferential surface of the connecting pipe 08 and the outer circumferential surfaces of the cylindrical portions 04 and 05. Clips 010 are engaged with the outer circumferential surfaces of the cylindrical portions 04 and 05 so as to be maintained in contact with the opposite ends of the connecting pipe 08.
The connecting pipe 08 in the cooling water passage structure mentioned above is formed of rigid metal such as aluminum or steel. Accordingly, even though the O-rings 09 are interposed therebetween, it is necessary to increase a working accuracy of the outer circumferential surfaces of the cylindrical portions 04 and 05 and a working accuracy of the inner circumferential surface of the connecting pipe 08.
In many cases, bosses 011 are provided for connection with cylinder heads (not shown) or other projections for mounting auxiliaries or sensors that project from the outer circumferences of the cylinders 01 and 02. In cutting the outer circumferential surfaces of the cylindrical portions 04 and 05, the cylinders 01 and 02 are rotated about the center line of the cylindrical portions 04 and 05 in many cases. In this cutting work, there is a possibility that the bosses 011 or the projections may come into contact with a cutting tool located on the outer circumferences of the cylindrical portions 04 and 05, thus hindering a smooth cutting work of the cylindrical portions 04 and 05.
When a cylinder scissors angle defined by the cylinders 01 and 02 is small, the projection lengths of the cylindrical portions 04 and 05 are limited, and the engagement lengths of the cylindrical portions 04 and 05 with respect to the connecting pipe 08 are also reduced, causing a difficulty in maintaining water tightness.
The present invention relates to an improvement in a cooling water passage structure in a water cooled type V-shaped internal combustion engine that solves the above problems. In the cooling water passage structure in the water cooled type V-shaped internal combustion engine, the improvement provides cylindrical portions that communicate with cooling water passages in opposed cylinders forming a V-shape project substantially in one straight line into a V-shaped space defined between said opposed cylinders. The opposite end portions of a connecting pipe engaged in said cylindrical portions are water tight.
In the present invention, contact portions of each cylindrical portion with respect to the connecting pipe are formed on the inner circumferential surface of each cylindrical portion. Accordingly, the length of the inner circumferential surface of each cylindrical portion from the front end to the bottom of the cylindrical portion is constructed larger than the projection length of each cylindrical portion projecting from the outer surface of the corresponding cylinder. As a result, even though the cylinder scissors angle between the opposed cylinders is small, and the projection length of each cylindrical portion is accordingly short, a sufficient engagement length of the connecting pipe with respect to each cylindrical portion can be ensured. Thus, the present invention is applicable also to a V-shaped internal combustion engine having a small cylinder scissors angle between the cylinders.
In the present invention, a connecting portion of each cylindrical portion with respect to the connecting pipe is the inner circumferential surface of each cylindrical portion. Accordingly, even though a projection or the like is present in the vicinity of each cylindrical portion on the outer surface of each cylinder, cutting work on the inner circumferential surface of each cylindrical portion can be easily performed by inserting a cutting tool into each cylindrical portion without hindrance of the projection and rotating each cylinder about the center line of each cylindrical portion.
In the present invention, even when the pressure of cooling water flowing in the cylindrical portions and the flexibility of the connecting pipe increases, the flexible connecting pipe is expanded by the increased pressure of the cooling water to increase the pressure contact with the inner circumferential surfaces of the cylindrical portions, thereby ensuring water tightness in a cooling water system.
In the present invention, even if there are variations in the working accuracy of the inner circumferential surfaces of the opposed cylindrical portions or locating accuracy of the opposed cylinders, the variations can be absorbed by elastic deformation of the flexible connecting pipe. The flexible connecting pipe can be engaged into the cylindrical portions easily and securely.
In the present invention, the connecting pipe can be stably engaged into the cylindrical portions.
In the present invention, water tightness of an engaged portion of each cylindrical portion with respect to the connecting pipe can be improved.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.